DFT evaluation of the effects of OH, NH2 and Br substituents on the properties of 2,2 '-bipyridine derivatives

A theoretical assessment of the effects of the OH, NH2 and Br substituents on the properties of 2,2'-bipyridine has been carried out using density functional theory approach. The substituents were found to alter both electronic and structural properties of substituted 2,2 '-bipyridine with the inductive and resonance effects playing significant roles. For the relative stability study, an order of ortho > para > meta was predicted for each set of the 2,2'-bipyridine derivatives with the ortho conformers being more stable by 4.62, 6.54 and 2.18 kcal/mol than the meta counterparts of the hydroxo, amino and bromo configurations respectively. On the part of electronic property, the electron donating / withdrawing tendency of the substituents was crucial in making electrons available to the bipyridine system. A general reduction in HOMO - LUMO energy gap was noticed upon substitution with the NH2 substituent having greater effect. Furthermore, the calculated reactivity parameters of the 2,2'-bipyridine were altered by substitution with - OH and -NH2 substituents causing reduction in ionization potential (IP) and absolute electronegativity (chi) while the - Br substituent did otherwise. For the solubility simulation, a more negative Delta G(solution) was predicted for the hydroxo and amino derivatives at the para position, but reverse was the case for the bromo counterpart. In the case of the optical property, the range separated Time-dependent (LC-TDDFT) calculation revealed that the shifts in absorption lambda(max) caused by the substitution is both substituent and position dependent.